1. Field of the Invention
The present invention generally relates to a semiconductor substrate, and more particularly, the present invention relates to a damascene interconnection structure.
This application is a counterpart of Japanese application Serial Number 163304/1998, filed Jun. 11, 1998, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
In general, it is difficult to form a pattern by etching a Copper (Cu) interconnection. In a formation of the Cu interconnection, an insulating layer such as SiO2 or BPSG is formed on a semiconductor substrate. Then, a recess is formed in the insulating layer so as to shape the Cu interconnection. Then, Cu is buried in the recess. As a result, the Cu interconnection buried in the recess is a so-called damascene interconnection, which is formed on the semiconductor substrate.
Such a damascene interconnection is formed as shown in FIG. 1A–FIG. 1D. FIG. 1A–FIG. 1D are cross sectional views showing a damascene interconnection structure of a conventional art.
A first interconnection pattern recess is formed using photolithography technique and etching technique in a first SiO2 film 12 having a thickness of 1 μm on the semiconductor substrate 10. Then, a barrier layer 16 such as a TiN is formed on the first SiO2 film 12 in the first interconnection pattern recess. Then Cu is formed on the entire surface and the Cu is polished with alkaline solution having a colloidal-silica, so called CMP (chemical mechanical polishing) method. As a result, a first interconnection including a main interconnection 19 which is made up of the Cu, as shown in FIG. 1A. A second SiO2 film 22 having a thickness of 1 μm is formed on the first SiO2 film 12 where the first interconnection 18 was formed. Then, a through hole 55 is formed in the second SiO2 film 22 so that a center portion of an upper surface of the first interconnection 18 is exposed, as shown in FIG. 1B.
Then, Cu is formed on the entire surface using sputtering technique, and the Cu is polished using the CMP method. As a result, a second interconnection 28 including a main interconnection 29 which is made up of the Cu, as shown in FIG. 1D.
In the conventional art of the method for forming the interconnections, it is desirable to avoid a problem wherein the Cu transfers from a portion connected to the second interconnection due to electromigration, whereby a void is formed at the connected portion, and the first interconnection is disconnected from the second interconnection.